MicroRNA in situ hybridization in the human entorhinal and transentorhinal cortex

Peter T Nelson

doi:10.3389/neuro.09.007.2010

Abstract

MicroRNAs (miRNAs) play key roles in gene expression regulation in both healthy and disease brains. To better understand those roles, it is necessary to characterize the miRNAs that are expressed in particular cell types under a range of conditions. In situ hybridization (ISH) can demonstrate cell- and lamina-specific patterns of miRNA expression that would be lost in tissue-level expression profiling. In the present study, ISH was performed with special focus on the human entorhinal cortex (EC) and transentorhinal cortex (TEC). The TEC is the area of the cerebral cortex that first develops neurofibrillary tangles in Alzheimer's disease (AD). However, the reason for TEC's special vulnerability to AD-type pathology is unknown. MiRNA ISH was performed on three human brains with well-characterized clinical and pathological parameters. Locked nucleic acid ISH probes were used referent to miR-107, miR-124, miR-125b, and miR-320. In order to correlate the ISH data with AD pathology, the ISH staining was compared with near-adjacent slides processed using Thioflavine stains. Not all neurons or cortical lamina stain with equal intensity for individual miRNAs. As with other areas of brain, the TEC and EC have characteristic miRNA expression patterns. MiRNA ISH is among the first methods to show special staining characteristics of cells and laminae of the human TEC.

Highlights

Alzheimer’s disease (AD) is a prevalent neurodegenerative disease that culminates in severe deficits in cognition and autonomy
We chose to study four miRNAs that are expressed in human brain: (1)miR-107, which we have shown may be relevant to AD pathogenesis and traumatic brain injury, and which may be involved in metabolic regulation (Wilfred et al, 2007; Wang et al, 2008; Redell et al, 2009; Tang et al, 2009)
Note that the Thioflavine S-stained neurofibrillary tangles (NFTs)-bearing neurons are present in a band of cells that are relatively lacking in In situ hybridization (ISH) stain for both miR-124 and miR-320

Summary

Introduction

Alzheimer’s disease (AD) is a prevalent neurodegenerative disease that culminates in severe deficits in cognition and autonomy. Brains afflicted by AD contain two different neuropathological hallmarks – neurofibrillary tangles (NFTs) and neuritic amyloid plaques (NPs) The National Institute on Aging, and Reagan Institute Working Group on Diagnostic Criteria for the Neuropathological Assessment of Alzheimer’s Disease (1997). Most clinico-pathological correlation studies indicate that cortical NFT density, assessed by Braak staging (Braak et al, 1993) or other means, is the parameter best correlated with the severity of AD cognitive impairment (Arriagada et al, 1992; Nelson et al, 2007b, 2008a,b, 2009b; Sonnen et al, 2007). In the first stages of the disease, NFTs are observed in medial temporal lobe structures (Braak and Braak, 1991)

Methods

Results

Conclusion